The present invention relates to a liquid ejecting apparatus, and particularly to a liquid ejecting apparatus provided with a liquid ejecting head which can be utilized as a recording head that ejects ink to a recording medium to perform recording, a color material ejecting head used in manufacture of a color filter of a liquid crystal display, an electrode material (electric conducting paste) ejecting head used in formation of electrodes of an organic EL display and FED (face light emitting display), a bioorganic matter ejecting head used in manufacture of biochip, or a sample ejecting head used as a precise pipette.
As a representative example of the liquid ejecting apparatus, an ink jet recording apparatus is known. This ink jet recording apparatus includes a recording head mounted on a carriage which reciprocates in a main scanning direction, and a recording medium feeding unit which feeds a recording medium such as a printing sheet intermittently in a sub-scanning direction by the predetermined amount, and ejects an ink droplet from the recording head during moving the recording head in the main scanning direction thereby to perform recording. In the ink jet recording apparatus, as known well, ink is pressurized in a pressure generating chamber at a predetermined pressure, and the ink is ejected from a nozzle opening in a nozzle forming face on the basis of its pressure to the recording medium as an ink droplet having a controlled size. Accordingly, ink ejection characteristic of the recording head from the nozzle opening must be kept constant, and variation of the ink ejection characteristic causes deterioration of recording quality.
The ink ejection characteristic of the recording head varies because of nozzle clogging caused by adhesion of hardened ink and dust onto the nozzle forming face, and intrusion of air bubbles from the nozzle. Therefore, in order to keep the ink ejection characteristic of the recording head constant, the ink jet recording apparatus is provided with an ejection characteristic keeping device which removes each reason of the variation of the ink ejection characteristic, and keeps the ejection characteristic of the recording head.
The ejection characteristic keeping device usually includes a capping unit firstly. In no-recording, the nozzle forming face is sealed by this capping unit to isolate the nozzle opening from the outside, whereby dry of ink is suppressed, and increase of ink viscosity is suppressed.
Further, even in case that the nozzle forming face is sealed by the capping unit, clogging of the nozzle opening and mixing of air bubbles into an ink flowing passage can be not prevented completely. Therefore, in order to remove the clogging of the nozzle opening and the mixed air bubbles, the ejection characteristic keeping device includes secondarily a suction unit which can suck and exhaust the ink from the nozzle opening forcedly. This suction unit, in a state where the nozzle forming face is sealed by the capping unit, applies a negative pressure to the nozzle opening, and sucks and exhausts the ink from the nozzle opening forcedly thereby to remove the clogging and the mixed air bubbles. The forced sucking and exhausting processing of ink by this suction unit is called as cleaning. Usually, in case that a recording operation is restarted after the recording apparatus has been stopped for a long time, or in case that a user recognizes the deterioration of quality of a recording image and operates a special switch on an operational panel, cleaning is executed.
When the forced sucking and exhausting processing of ink is thus performed by the suction unit, the ink frequently scatters on the nozzle forming face of the recording head is adhered thereon, and meniscus of ink in each nozzle opening is disordered. Further, foreign matters are easy to be attached on the nozzle forming face of the recording head with the passage of time. Therefore, the ejection characteristic keeping device includes thirdly a wiping member which wipes the nozzle forming face according to necessity. This wiping member has a wiping member made of elastic material such as rubber, and the base end side of the wiping member is held and supported by a holder. The edge portion on the leading end side of the wiping member or its surrounding portion is elastically pressed against the nozzle forming face and moved relatively thereby to clean the nozzle forming face. The cleaning operation by the wiping member is called as a wiping operation. By this wiping operation, the ink and dust attached onto the nozzle forming face are wiped, and further this operation performs a part of making the meniscus of ink in each nozzle opening uniform, that is, a part of stabilizing the meniscus of ink. In the thus constructed ink jet recording apparatus, in order to improve fixability of ink onto the recording medium, recently a recording method in which a fixing liquid that acts on ink to heighten color forming ability is ejected in addition to the ink is being developed. Namely, in this double liquid fixing system, the fixing liquid (second liquid) which has cationic resin as a main component and does not include ink is ejected onto the recording medium in addition to the ink (first liquid), whereby electric stability of dispersion medium (usually, anionic resin is used.) of pigment included in the ink is changed to urge the cohesive power of the pigment, and the fixability of ink onto the recording medium surface is improved. Hereby, improvement of glossiness in ink jet paper and improvement of color forming ability in plain paper are simultaneously realized.
In the double liquid fixing system, in case that the first liquid and the second liquid are mixed, the cohesion of the pigment is produced due to the properties of these liquids, so that clogging of the nozzle is caused. Accordingly, not only in the ink cartridge but also around the recording head (for example, on the nozzle forming face), mixing of these liquids must be avoided. Therefore, in the double liquid fixing system, it is necessary to constitute the flowing passage and the nozzle opening separately between the ink and the fixing liquid.
By the way, the related ink jet recording apparatus includes the ejection characteristic keeping device, and this device performs the wiping operation of the nozzle forming face of the recording head and the suction operation in the state where the nozzle forming face is sealed (capped). In this wiping process, if the first liquid and the second liquid which are attached onto the nozzle forming face are mixed, the cohesion of the pigment is produced on the nozzle forming face, and clogging is produced in the nozzle opening, which causes ejection trouble. In order to avoid such the unintended mixing state of the first liquid and the second liquid, it is effective to set the recording heads separately or set the wiping members separately. However, this complicates the constitution of the apparatus and increases the number of parts, so that this is not a realistic solving means in the ink jet recording apparatus in which many functional parts have been already collected in the limited space.
Further, also in the sucking operation, in case that the both liquids are mixed in the cap, cohered matters remain in the cap or clogging of the suction port that is an outlet of the waste ink is caused. Particularly, in case that the both liquids are filled in the cap in the state where they are mixed, there is possibility that the cohered matters are attached onto the nozzle forming face and clogging of the nozzle opening is caused similarly to in case of wiping. Also in this case, it is effective to set the recording heads and the capping units separately between the first liquid and the second liquid (for example, refer to JP-A-8-281968). However, this causes complicacy of the apparatus constitution and increase of the number of parts.
Further, in an ink jet recording apparatus so constructed that ink of plural colors are ejected from a single recording head, a technology of defining the inside of the cap to prevent color mixing is proposed (for example, refer to JP-A6-191061). However, this ink jet recording apparatus does not relate to the double liquid fixing system, and a suction port is provided for each defined portion. Therefore, since waste ink passages connecting the cap and the sucking unit must be provided separately, the constitution becomes complicated, which is contrary to the above requirement.
The problem of mixture in the double liquid fixing type ink jet recording apparatus is produced also in another liquid ejecting apparatus utilizing the liquid ejecting head such as the precious pipette which ejects a test liquid (sample) and the specified reagent having reactivity to the test liquid.